Conventionally, in electronic part apparatuses such as semiconductor apparatuses and the like, an element is encapsulated for the purpose of protecting elements such as transistors, IC and the like from the outer environments, and making mounting on a substrate easy. In the field of this element encapsulation, encapsulation with a resin is mainly used from the standpoints of productivity, cost and the like and encapsulating molding materials using thermo-setting resins are widely used. Particularly, encapsulation methods such as transfer molding using an encapsulating molding material in the form of powder, and the like are excellent in economy and productivity, and said to be suitable for mass production. Encapsulating molding materials in the form of powder are often tablet-formed into a cylindrical encapsulating molding material tablet of weight and dimension corresponding to the requirements by clients.
In encapsulating an element of an electronic part apparatus using an encapsulating molding material tablet, reduction in generation of voids inside is required for improving its molding property and reflow crack resistance. Therefore, high density of an encapsulating molding material tablet is required, and the forming pressure in forming a tablet tends to be increased.
However, when the forming pressure in forming a tablet increases, an encapsulating molding material easily adheres to the punch surface of a tablet forming machine. When a biphenyl type epoxy resin excellent in reflow crack resistance is used as an encapsulating molding material, an encapsulating molding material easily adheres to the punch surface irrespective of the forming pressure in forming a tablet. When an encapsulating molding material is partially adhered to the punch surface of a tablet forming machine, there occurs a problem of production of an encapsulating molding material tablet of which surface is partially missed. In generation of such adhesion, a tablet forming machine is stopped, the punch surface is manually cleaned to remove the adhered substance, leading to remarkable decrease in productivity.
As a method of preventing adhesion of an encapsulating molding material to the punch surface of a tablet forming machine, a release agent has been tried to be baking-applied on the punch surface of a tablet forming machine, leading, however, to only an insufficient effect. Further, a method of adding a release agent to an encapsulating molding material and a method of coating a silicone-based release agent having specific thickness on the punch surface (JP-A No. 9-193149) have been suggested, however, there are problems regarding the reliability of an encapsulating molding material such as poor appearance of stain observed on the appearance of a tablet, lowering in reflow resistance, and the like though adhesion is partially improved.
The present invention has been accomplished in view of such conditions, and an object thereof is to provide a method of producing an encapsulating molding material tablet by which adhesion of an encapsulating molding material to the punch surface of a tablet forming machine can be reduced, an encapsulating molding material tablet produced by this method, and an electronic part apparatus equipped with an element encapsulated using this encapsulating molding material tablet.